Department: University of Delaware, Department of Materials Science and Engineering
Publisher: University of Delaware
Date Issued: 2012
Abstract: An alternative and new approach to making hydroxide exchange membranes (HEM’s)
for hydroxide exchange membrane fuel cells (HEMFC) via thiol-ene photocrosslinking
polymerization is demonstrated. Specifically a novel difunctional vinyl
monomer, quaternary phosphonium bisphenyl allyl ether chloride (QPBPAE-Cl), was
successfully synthesized in a simple and cost effective three-step process. This
synthesis protocol enables the interchangeability of the cationic functional group in the
last synthesis step to readily assess hydroxide conductivity differences. This novel
charged monomer was successfully photo-crosslinked in a ternary system consisting
of 1,6-hexanedithiol and 1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione
(TATATO, a trifunctional ‘ene’ for crosslinking) to form the HEM. While the formed
HEMs exhibit low hydroxide conductivity, they possess robust mechanical properties
and excellent alkaline stability in 1M KOH for 48 hrs. The hydroxide conductivity for
200 – 290 μm thick specimens was 1.4 and 2.6 mScm-1 for a QPBPAE-Cl to
TATATO ratio of 1:1.5 and 1:2, respectively, and a stoichiometric balance of thiol
monomer. The swelling ratio of the HEM was 8.25% and 8.89% in water and the
measured tensile strength was 57.73 and 45.28 MPa for a QPBPAE-Cl to TATATO
ratio of 1:1.5 and 1:2, respectively.
